How Much Lumber Will I Get From My Logs?
There are many factors that will influence how much useable lumber you will get from your logs. The primary factors are log diameter and length, but the quality of the logs will also influence the lumber yield. Some of these quality factors include wood rot, sweep (curve), foreign objects, shake (cracks) and damage done when the trees are felled.
Lumber volume is measured in "board feet". One board foot is defined as 144 cubic inches. 1"x12"x1' equals one board foot (bf). So does 2"x6"x1'. For example a 1"x12" ten feet long contains 10bf. A 1"x6" ten feet long contains 5bf.
There are three common methods for estimating lumber yield from a log. The three methods are Doyle, Scribner and International. Each method uses a formula to calculate the number of board feet of lumber in a given size log. For a bandmill like the Wood-Mizer, the International scale usually gives the most accurate estimate of lumber yield. However all of these scales assume straight, healthy logs. Any defect in the logs may reduce the amount of lumber produced. Your can use the calculator at this link to give you a rough idea of the the amount of lumber you can expect from your logs.
Your New Lumber
The lumber we produce will be rough sawn and green. "Rough sawn" means it will have blade marks on the surface of the wood. Lumber from the Wood-Mizer is generally fairly smooth and is suitable for any uses where rough sawn lumber is acceptable. If you plan to use it for furniture, cabinets, flooring, etc. it will need to be planed smooth.
"Green" means that the wood still contains the moisture it had in it when it was alive.
For most purposes it needs to be dried. Lumber may either be dried in a kiln or it may be air dried. Air drying takes more time - one month to a year or more depending on species and thickness. Pine and cedar usually dry fairly quickly (1 to 2 months). Hardwood typically takes longer, usually 6 months to a year. Read the section below for more information on air drying lumber.
Air Drying Your Lumber
Lumber milled from a fresh cut log has a lot of water in it. Depending on the species, some wood has more weight in water than it does in dry material weight! The water is removed by evaporation.
Air drying requires good air circulation around the boards. To achieve this, lumber is stacked in a way that allows good air flow over and under both faces of each board. This carries the moisture off. Each board in a layer must be the same thickness. Each layer of boards is supported from the one below by spacers called stickers. Stickers are typically just wooden sticks about one inch thick. They can be a little thicker or thinner as long as they are all the same thickness. The stack needs to be raised above the ground, even, and well supported for it's entire length. Drying stacks of lumber are quite heavy! Freshly cut lumber should be stickered within 24 to 48 hours after cutting. Otherwise it may begin to mold or mildew, particularly in warm weather.
Stickers need to be placed at regular intervals and also at the ends of the boards; spacing should be from 16" to a maximum of 24" apart. Stickers need to be placed directly one above the other in order to transfer weight directly to the supports under the stack. If this is not done, the boards will not dry flat.
I can saw stickers for you from the edgings of your green wood if you desire. For some wood that is prone to staining, it may be best to use dry stickers. If you wish to use dry stickers and do not have your own, I can provide dry stickers for $0.25 each.
The height of the stack is not critical, other than for comfort and safety purposes. The width of the stack is much more important. A stack too wide will not allow enough air flow through it and will not dry properly. Four feet is usually a good width to ensure adequate air movement. Similarly if the stack is placed against a wall or inside a closed building, air will not be allowed to flow unimpeded and the lumber will not dry properly. If good air movement is not achieved, the wet lumber may mold or mildew causing the lumber to turn black or gray. For species that tend to stain easily, it may be helpful to set up a fan to blow on the stack for the first few days to help dry the surface of the lumber more quickly.
If the lumber is to be stacked outside, the top of the stack should have a row of stickers on it, followed by a rigid covering somewhat larger than the stack. Many people use sheets of tin. That keeps direct sunshine and rain off the stack. It should also be well weighted to help prevent the upper boards from moving as they dry. If the lumber is stacked under a shelter the covering will not be required, but it still needs to be weighted to ensure the top boards remain flat as they dry. Just keep in mind that if you are stacking under a shelter, make sure you have good air movement - open shelters are better than enclosed barns for this purpose.
The diagram below is an excellent representation of the suggested practice for air-drying lumber.
Source: A Consumers' Guide to Buying and using Locally Produced Lumber, New York Department of Environmental Conservation and Black River - St.Lawrence Resource Conservation and Development Council.